package com.yanliang.SqlSession;

import com.yanliang.pojo.Configuration;
import com.yanliang.pojo.MappedStatement;

import java.beans.IntrospectionException;
import java.lang.reflect.*;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;

/**
 * SqlSession 实现类$
 *
 * @Author : yanliang
 * @Data : 3/25/2020 7:08 PM
 */
public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws IllegalAccessException, IntrospectionException, InstantiationException, SQLException, InvocationTargetException, NoSuchFieldException {
        // 调用执行器 完成sql的执行
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        List<Object> queryList = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) queryList;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws IllegalAccessException, IntrospectionException, InstantiationException, SQLException, InvocationTargetException, NoSuchFieldException {
        List<Object> objects = selectList(statementId, params);
        if (objects.size() == 1) {
            return (T) objects.get(0);
        }
        else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public int update(String statementId, Object... params) throws NoSuchFieldException, IllegalAccessException, SQLException {
        // 调用执行器 完成sql的执行
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return simpleExecutor.update(configuration, mappedStatement, params);
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层还是去执行JDBC代码
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();
                String statementId = className+"."+methodName;
                MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
                SqlCommandType sqlCommandType = mappedStatement.getSqlCommandType();
                // 查询操作
                if (sqlCommandType.equals(SqlCommandType.SELECT)) {
                    // 准备参数2：params:args
                    // 获取被调用方法的返回值类型
                    Type genericReturnType = method.getGenericReturnType();
                    // 判断是否进行了 泛型类型参数化
                    if(genericReturnType instanceof ParameterizedType){
                        List<Object> objects = selectList(statementId, args);
                        return objects;
                    }
                    return selectOne(statementId,args);
                }
                else {   // 更新 插入 删除 操作
                    return update(statementId, args);
                }
            }
        });
        return (T) proxyInstance;
    }
}
